MAINTAINING SOIL FERTILITY 297 



of the old-time fallowing was that it promoted 

 weathering and so increased the amount of 

 soluble plant food in the few inches of surface 

 soil that were stirred by the clumsy tools of that 

 time. Modern tillage tools prepare the soil so 

 thoroughly and deeply that a larger area is laid 

 under tribute, and weathering, and other agencies 

 that increase fertility, have a better opportunity to 

 work. There are still occasions, however, when 

 fallowing is beneficial and sometimes very essential. 



Fallowing to Store Water. The value of fallow- 

 ing in American farming is chiefly in storing 

 water in the soil and cleaning the land of weeds, 

 rather than in increasing the amount of soluble 

 plant food in the soil. In the semi-arid and 

 arid sections of the West where "dry farming" 

 is practised, fallowing is often indispensable. The 

 land is cropped one year and fallowed the next, or it 

 is fallowed one year in three. Fallowed land is 

 plowed and harrowed so that the soil will receive 

 and hold all the rainfall. Where the rainfall is 

 less than ten to fifteen inches such a proceeding 

 may be absolutely necessary. King found that 

 the fallowed part of a certain field contained 203 

 tons more water per acre in the spring succeeding 

 the fallow than the part that was not fallowed. 

 Even at the end of the season, after large crops of 

 grain had been taken from the land, it contained 

 179 tons of water more than the unfallowed land. 

 This shows that summer fallowing has a marked 

 and lasting influence on the moisture content of 

 soils. It is likely that fallowing to store water will 

 always be practised in America far more than 

 fallowing for any other specific purpose. 



Fallowing to Set Free Plant Food. Fallowing 

 increases the amount of available plant food in the 



